The complete loop
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What you will learn
By the end, you can tell whether a bulb will light by checking for a complete loop, and sort conductors from insulators.
Dark tent. Noah clicks the torch: nothing. The batteries are in and the bulb looks fine. Then he spots it: a bent metal spring no longer touches the battery. There is a gap, so the loop is broken.
Read the explanation
Electricity flows only around a complete loop: a circuit. A cell (a battery) pushes it, wires carry it, and a bulb or buzzer uses it. A switch opens or closes a gap. Any gap anywhere, and the whole circuit stops.
- Conductors let electricity through: metals such as copper, steel and aluminium.
- Insulators block it: plastic, rubber, wood and glass.
- More cells, all facing the same way, make a bulb brighter.